High-intensity light induces anthocyanin production in wild-type Arabidopsis leaves, but this induction is largely abolished in the chlorotic leaf tissues of AKR (ankyrin repeat-containing protein)-deficient plants. The steady-state mRNA levels of three anthocyanin biosynthetic genes, CHI, CHS and DFR, did not increase in response to high-intensity light treatment in chlorotic leaf tissues, whereas they increased several fold in green leaf tissues. There is a good correlation between anthocyanin production and transcript levels of anthocyanin biosynthetic genes, especially DFR, in green leaf tissues. In contrast, the transcripts of TCH2 and TCH3 that encode for calmodulin-related proteins and GPA that encodes for the ฮฑ subunit of the trimeric G protein were much higher in chlorotic leaf tissues than those in green leaf tissues. These data suggest that the AKR-deficiency could increase gene expression in one signal transduction pathway and at the same time repress gene expression in another signal transduction pathway, which alludes to a possible mechanism for AKR involvement in chloroplast development. ยฉ Elsevier, Paris Anthocyanin / Arabidopsis thaliana / chlorosis / high-intensity light / signal transduction AKR, Arabidopsis gene encoding for ankyrin repeat-containing protein / LHC, light harvesting complex